Abstract
•The hexacoordinated ligand containing quinoxaline backbone along with their Cuii-based complexes with various counter anions were synthesized and their structures were determined.•The exact geometry of most Cuii-complexes was demonstrated by processing the PXRD data using a computer program specializing in the structural analysis of metallic complexes.•Mimicry of copper oxidase proteins such as catechol oxidase and phenoxazine synthase has been studied.•The stereochemistry of copper(II) complexes and their oxidase biomimetic catalytic activity was tuned by the counter anion included in the copper(II) oxidase mimics.•The driving force of the studied catalytic reactions was determined based on the electrochemical data and the effect of the driving force (λ or–ΔG°) on the catalytic activity was addressed.
The hexadentate ligand containing quinoxaline backbone along with its Cu(II) -based complexes with various anionic ligands were synthesized and their structures were determined. Molecular formulae were assigned based on the data of both elemental analysis and the electrical conductivity in DMF solutions. Spectroscopic and magnetic measurements were performed to achieve the final structural properties. The exact geometry of the synthesized Cu(II) complexes was demonstrated by processing the PXRD data using a computer program specializing in the structural analysis of metallic complexes. The anionic ligands included in the complex molecule adjust the stereochemistry of the central Cu(II) ion. In this regard, the halogeno ligands direct the octahedral environment while the nitrato, acetato and perchlorato ligands adjust the dsp3 hybridization of the trigonal bipyramidal stereochemistry. Mimicry of copper oxidase proteins such as catechol oxidase and phenoxazine synthase has been studied. The oxidase biomimetic catalytic activity was tuned by the anionic ligands included in the Cu(II) oxidase mimics. Kinetic measurements allowed the determination of relevant parameters such as Vmax, kcat, KM and the ratio kcat/KM. The potential catalytic reaction sequences have been suggested based on the results of kinetic investigations. The driving force of the studied catalytic reactions was determined based on the electrochemical data and the impact of the driving force (λ or–ΔG°) on the catalytic activity was addressed.
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